The invention relates to an anti-locking brake control system of the type having wheel velocity pickups, which provide signals to an evaluation circuit, which provides signals to brake pressure control valves. The evaluation circuit controls relief of pressure on the basis of wheel retardations and accelerations occurring in rapid succession.
When driving over rough roads a constant alternation takes place between the loading and unloading of the wheels. When the brakes are applied, therefore, a rapid succession of strong retardations and accelerations of the wheel circumference are produced. The electronic anti-locking brake control system therefore produces a frequent relieving of the brake pressure. This results in an underbraking of the vehicle.
To avoid this disadvantage it is known to suppress the relief of the brake pressure on a wheel for a period of time at the end of the reacceleration of this wheel.
It is furthermore known to trigger a rapid pressure increase in the event of great accelerations of the wheel circumference, which is intended to compensate for the previous pressure relief.
A sufficient increase in the brake pressure during the period when the wheel is reaccelerating is not possible in most cases, since, even on smooth roadways, strong accelerations occur which, in the event of rapid pressure rises such as would be necessary on rough road surfaces, can lead to unwanted disturbances caused by resonance.
Furthermore, it is known to determine the maximum wheel acceleration in the reacceleration phase of the wheel and increase the pressure relief threshold according to the magnitude of this acceleration, as disclosed in GB-A No. 2151732, to which U.S. Pat. No. 4,701,855 to Fennel corresponds.